Further integration of the type-A-choking-oriented unified model for fast fluidization dynamics

• Sub-model of cluster rebound was proposed for average solids holdup in dense bottom.
• Heights of built-up dense bottom were well correlated using the concept of elutriation.
• Sub-models for transition/acceleration zones were established with momentum balance.
• Model predicted axial solids holdup distribution under various operating conditions.
• Minimum solid flux was semi-analytically determined: saturated with solids at 3ut.

As a supplementary paper, this article answers some questions that remain unsolved in our previous work — “A type-A-choking-oriented unified model for fast fluidization dynamics”, namely how to predict the axial solids holdup distribution and the minimum solid flux for fast fluidization. Starting from the physico-mathematical model of “cluster rebound at the dense bottom” proposed by the authors, the critical value of solid flux Gsrb distinguishing two different types of axial solids holdup distributions was determined. Then, the height of built-up section having nearly constant solids holdup in the bottom region was correlated with the experimental data in the literature using the concept of elutriation for the extra solid flux Gs–Gsrb. The models for the transition zone between the built-up dense bottom and the fully developed upper dilute region, and for the acceleration zone prior to the built-up dense bottom of a classical fast bed, were established in accordance with the principle of momentum flux balance. The integrated model predicted successfully the axial solids holdup distributions of Issangya's experiments under extremely wide operating conditions, covering dilute phase transport, the premature fast bed, the classical fast bed, and the high-density fast bed. The prediction method of the minimum solid flux for fast fluidization Gsm was semi-analytically deduced, indicating that Gsm can be estimated using the revised Yang's formula at the superficial gas velocity of 3ut. Finally, some important assumptions and consequences of the unified model are discussed.

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